Question - The chances of collapse

[novice_strength]

Hi guys

I know theres obviously many factors to consider but what are the chances of the back (mine roof) collapsing on top of you?

Cheers

 

[The Lone Ranger]

Some mines will be more prone than others. Mines in sedimentary rock are probably more prone to collapse, but it also depends on they way they were mined, condition of roof props, amount of waste left in them, natural faulting of the rock. Chances of it happening, it does happen every now and then.

 

[Lord Oort]

Well that kinda depends on which mine you're in...

Genrally speaking its a case of risk assessment on the day. A few things to consider are

Are there a lot of props on the floor?
Has there been a recent fall?
Is the stone above you solid or like crazy paving?
Are there any lose bits?

That said, youre much more likely to get injured on your way to or from wherever youre going than when youre underground, You need to decide the amount of risk youre prepared to take and then act accordingly, if you dont like the way a particular bit of roof looks then dont walk under it.

E2A: Beat me to it TLR

 

[The Lone Ranger]

E2A: Beat me to it TLR

You reply was more comprehensive

Other thing you have to consider is the possibility of false floors, old timbers covering a void below. These are often covered in debris so you don't know you're stood onto of rotten wood and a void. Flooded sections can hide holes in the floor which will happily swallow you.

Best advice is do as much research as possible on the mine before hand, try and get hold of a survey and if in doubt bail out.

 

[cunningcorgi]

As two better authorities than me have said, it really all depends on the type of mine - coal, slate, iron, stone, etc.

You should usually be able to make a semi educated guess on the state of the mine when you see it. What is keeping the roof up for example ? Is it brick lined, is it propped, is spoil holding it up, etc. ? If propped, are they actually still propping ? If lined, is the lining still in place ?

All mines are different and if you think something looks really dodgy and unsafe, chances are, it probably is.

You can have add the added bonus in an iron mine of worrying about the roof and also the false floors that could be there !

 

[HughieD]

2.34%

 

[Lenston]

Dont let any fireworks off would be my advice

 

[The Lone Ranger]

I'd also contact the British Geological Survey Earthquake Seismology Team to see what the likelihood of a tremor occurring whilst you are underground

 

[wormster]

All of the above - AND LEAVE A CALL OUT!

 

[DaveFM]

Probably more chance of being hit by lightning, collapses can and do occur in many mines but the odds of a spontaneous collapse right over your head are negligible, providing you aren't disturbing any loose rock or props etc. The vast majority of mishaps in mines happened to the people who mined them, as they were actively involved in blasting or hacking out whatever was being mined. Gas or bad air is a far greater threat in general and a much less obvious danger if you don't have detection gear.
Picture from Cults mine where a partial collapse occurred but the girders are very thick and have stopped a total blockage.

 

[novice_strength]

Dont let any fireworks off would be my advice

We found fireworks sitting inside Cults once, safe to say ive never moved so quickly!

Probably more chance of being hit by lightning, collapses can and do occur in many mines but the odds of a spontaneous collapse right over your head are negligible, providing you aren't disturbing any loose rock or props etc. The vast majority of mishaps in mines happened to the people who mined them, as they were actively involved in blasting or hacking out whatever was being mined. Gas or bad air is a far greater threat in general and a much less obvious danger if you don't have detection gear.
Picture from Cults mine where a partial collapse occurred but the girders are very thick and have stopped a total blockage

Thats what i thought. That passage looks like a big nope haha

 

[Dan1701]

Personally, I'd say that as long as the roof looked OK and I didn't move anything then there would be little chance of it falling down. For the most part, stuff only moves if something gives it a push so the bigger threat would be your own bodyweight causing wooden flooring over voids (commonly called false floors) to collapse.

The other thing to be rather wary of is bad air of various sorts. If there isn't air flow through a mine then you're relying on diffusion to keep the air good, and the density of carbon dioxide is more than enough to overcome diffusion. That means that if there is carbon of any sort in the rocks (even amounts uneconomic to mine as coal) then the carbon oxidising is going to create carbon dioxide, which will end up sitting in the low spots. Iron ore is another danger; iron has several oxidation states and in a mine is never fully oxidised to iron-III oxide. Thus it tends to pull oxygen out of the air without releasing anything, meaning the oxygen levels drop and drop.

Carbon dioxide chokes you, it is detectable without equipment. Low oxygen just causes headaches and confusion, until you lose consciousness. Methane is explosive, and carbon monoxide deadly (as is hydrogen sulphide).

If you're making a habit of going into mines that aren't naturally ventilated, buy a gas detector and pay to have it properly serviced, then for goodness' sakes carry the thing! A miners lamp will tell you about low oxygen and methane (if you know how to read it and keep checking it), but there's nothing like the reassuring beep from a gas alarm to settle your nerves.

 

[cunningcorgi]

Carbon dioxide chokes you, it is detectable without equipment.

Do you mean undetectable ?

 

[wormster]

Seem to remeber years ago someone had 2 canaries "Scargill and Prescott" that used to go underground, more the reassuring cheep cheep than bleep bleep!!

 

[Dan1701]

Do you mean undetectable ?

No. I meant that carbon dioxide can be detected because low levels make you breathe more deeply, higher levels give a choking sensation.

Carbon dioxide is denser than air, so you'd expect to find it in the low spots in a cave or tunnel. This is one reason for carrying a gas detector on your belt, or a Davy lamp in your hand; the detection system encounters the gas whilst your head is still up and out of the way. If you encounter a pocket like this, don't bend down!

You're only really likely to hit carbon dioxide in either coal mines (in which case either you know the safety drill or you're an idiot) or if some twerp has lit a fire in the tunnel system previously. Carbon dioxide isn't as dangerous as carbon monoxide which is poisonous in low concentrations, nor is it as nasty as hydrogen sulphide.

Just take a known-working gas detector if you're going into anywhere except caves or stone mines.